1. Field of the Invention
The present invention relates to an air bypass valve failure detection device in a supercharging device of an engine, the supercharging device comprising: a first intake passage, a supercharger, a second intake passage, a throttle valve, and a third intake passage which are sequentially arranged from an upstream side to a downstream side in a flowing direction of an intake air flowing to a cylinder of the engine; a bypass passage bypassing the supercharger and connecting the first and second intake passages to each other; an air bypass valve provided in the bypass passage; the supercharging device outputting an opening command to the air bypass valve, when a rate of change in a throttle valve opening degree in a throttle valve closing direction is equal to or larger than a predetermined value.
2. Description of Related Art
Japanese Utility Model Publication No. 7-46737 discloses a device in which a blower (a compressor) of a turbocharger on an upstream side and a throttle valve on a downstream side are arranged in an intake passage of an engine, and a relief valve (an air bypass valve) is arranged in a relief passage (a bypass passage) that bypasses the blower of the turbo charger. When a difference between a detected value of an intake air quantity (or of a pressure of the intake passage between the blower and the throttle valve) and a time average value of the detected values is equal to or larger than a predetermined value at the time of sudden closure of the throttle valve, i.e., when the relief valve does not normally open and surging occurs in the intake passage, the device determines that a valve closing failure has occurred where the relief valve is stuck in a valve closing position.
The conventional device performs failure detection for the relief valve only on condition that the throttle valve has suddenly closed. Thus, there is a possibility that the device erroneously determines that the relief valve is normal even when the valve closing failure of the relief valve occurs. This is because, when the throttle valve suddenly closes and the failure detection is started, if an intake air quantity flowing through the intake passage is small, surging does not occur in the intake passage although the valve closing failure of the relief valve occurs, leading to a possibility that the device erroneously determines that the relief valve is normal only for the reason that surging has not occurred.